In conventional modular construction there is often a conflict between the need to provide flexible designs and a resulting redundancy of walls (double walls). That shortcoming consisted of having two bearing walls side-by-side results from the necessities and constraints of the system, particularly when the material is reinforced concrete. 3-dimensional “U” shaped (in vertical cross-section) modules are vertically cast. Therefore module can only have a maximum length in any dimension of about 3.7 meters (12 feet). Dropping the concrete any further during pre-cast pouring will cause separation of aggregate from the cement. Fisher, Method for Constructing Town Houses and the Like, U.S. Pat. No. 4,194,339 (Mar. 25, 1980) dramatizes the problem of the double walls which create more material and more cost. The challenge is to develop a system that allows for parallel bearing walls that eliminates the double walls and also eliminates the use of the “L” shaped module illustrated in Fisher, Construction System for Modular Apartments, Hotels and the Like, U.S. Pat. No. 6,393,774 (May 28, 2002) which has turned out to be physically cumbersome and therefore more expensive.